U.S. patent number 5,078,476 [Application Number 07/541,744] was granted by the patent office on 1992-01-07 for automatic backlight on/off control apparatus for liquid crystal display television.
This patent grant is currently assigned to Goldstar Co. Ltd.. Invention is credited to Jong K. Shin.
United States Patent |
5,078,476 |
Shin |
January 7, 1992 |
Automatic backlight on/off control apparatus for liquid crystal
display television
Abstract
An automatic backlight on/off control apparatus for use in a
liquid crystal display television includes a buffer amplifier, a
synchronizing signal detector, a switching controller, and a
backlight power controller for preventing electric power consumed
unnecessarily by turning the backlight off in case there is no
input of any video signal and turning the backlight on according to
the pulse signal of a pulse generating member only in case there is
a video signal input.
Inventors: |
Shin; Jong K.
(Kyungsangbook-Do, KR) |
Assignee: |
Goldstar Co. Ltd. (Seoul,
KR)
|
Family
ID: |
19287819 |
Appl.
No.: |
07/541,744 |
Filed: |
June 21, 1990 |
Foreign Application Priority Data
|
|
|
|
|
Jun 30, 1989 [KR] |
|
|
9531/1989 |
|
Current U.S.
Class: |
345/102;
348/E5.096; 348/E5.047; 348/730; 307/38; 348/790 |
Current CPC
Class: |
H05B
41/36 (20130101); H04N 5/44 (20130101); G09G
3/3406 (20130101); G09G 2330/022 (20130101) |
Current International
Class: |
H04N
5/44 (20060101); G09G 3/34 (20060101); H05B
41/36 (20060101); H04N 5/232 (20060101); G02F
001/13 (); H04N 005/74 () |
Field of
Search: |
;350/332 ;340/814
;307/268,261,38,40 ;358/59,236 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Miller; Stanley D.
Assistant Examiner: Mai; Huy K.
Claims
What is claimed is:
1. An automatic backlight on/off control apparatus for use in a
liquid crystal display television, which comprises:
a buffer amplifier means for buffer-amplifying and integrating
composite video signals entering a composite video signal input
terminal,
a synchronizing signal detecting means for detecting and outputting
a synchronizing signal according to a pulse output level of said
buffer amplifier means,
a switching control means for outputting a switching control signal
with a differential amplification applied after integrating the
output signal of said synchronizing signal detecting means, and
a voltage control means for supplying or cutting off a voltage of a
backlight voltage terminal to a backlight by switching operation in
accordance with the switching control signal of said switching
control means.
2. The automatic backlight on/off control apparatus of claim 1,
wherein the synchronizing signal detecting means is constituted by
connecting the output of said buffer amplifier means through a
first capacitor and a first resistor in the parallel connection to
the emitter of a first transistor of which base is applied with a
constant bias voltage, connecting the emitter of a second
transistor of which base is applied with a constant bias voltage to
the base of a third transistor as well as to the collector of said
first transistor through said first resistor, and connecting the
collector of said third transistor to the base of a fourth
transistor as well as to the emitter of said fourth transistor and
a second resistor through a third resistor in order that a high
potential is outputted only in case the output voltage of said
buffer amplifier means is below a determined level.
3. The automatic backlight on/off control apparatus of claim 1,
wherein the switching control means is constituted by connecting
the output of said synchronizing signal detecting means to the base
of a fifth transistor in the darlington connection with a sixth
transistor and a second capacitor, connecting the collector of
seventh and eighth transistors in the darlington connection to
which a constant bias voltage is applied to the bases of ninth and
tenth transistors as a constant current source and the collector of
said ninth transistor connecting the emitters of said seventh and
eighth transistors to the collector of an eleventh transistor to
which a constant bias voltage is applied, and connecting the
collector of said tenth transistor to a third resistor in order
that a low potential signal continues to be outputted from said
synchronizing detecting signal keeps on being outputted.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a backlight on/off control
apparatus for use in a liquid crystal display television
(hereinafter "LCD TV") and more particularly, to an automatic
backlight on/off control apparatus for automatically turning a
backlight on/off according to existing or non-existing of a
composite video signal.
2. Description of the Prior Art
Various types of backlight on/off control apparatuses having a
backlight which is turned on according to the pulse signals of a
pulse generating member are well known in the art. One of such
conventional backlight of/off control apparatuses for an LCD TV is
illustrated in FIG. 1. As shown in FIG. 1, since a transistor
TR.sub.1 is turned on or off according to pulse signals of a pulse
generating member 1, the voltage of a backlight voltage terminal
Vcc is induced in the second winding of a transformer T, which
causes a first capacitor C1 to be charged. The charged voltage of
the capacitor C1 is applied to a backlight 2 through a second
capacitor C.sub.2 to turn on the backlight 2. However, such
conventional backlight on/off circuit includes the backlight 2
turned on according to the pulse signals of the pulse generating
member 1 regardless of existing or non-existing of a video signal.
Therefore, such conventional backlight on/off circuit has a
drawback so that unnecessary power consumption increases.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an
automatic backlight on/off control apparatus for use in an LCD TV
which prevents electric power from being unnecessarily consumed by
turning a backlight off in case there is no input of any video
signal while the backlight turns on according to the pulse signals
of the pulse generating member only in case there is a video signal
input.
Another object of the present invention is to provide an improved
backlight on/off control apparatus for amplifying composite video
signals, detecting a synchronizing signal out of the composite
video signals, determining whether the video signal is inputted or
not according to the synchronizing signal being detected or not,
and supplying or cutting off the electric power to the backlight
according to the determination of the existing or non-existing of
the video signal input.
Other objects and further scope of applicability of the present
invention will become apparent from the detailed description given
hereinafter. It should be understood, however, that the detailed
description and specific examples, while indicating preferred
embodiments of the invention, are given by way of illustration
only, since various changes and modifications within the spirit and
scope of the invention will become apparent to those skilled in the
art from this detailed description.
Briefly described, the present invention relates to an automatic
backlight on/off control apparatus for use in a liquid crystal
display television includes a buffer amplifier, a synchronizing
signal detector, a switching controller, and a backlight power
controller for preventing electric power consumed unnecessarily by
turning the backlight off in case there is no input of any video
signal and turning the backlight on according to the pulse signal
of a pulse generating member only in case there is a video signal
input.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the
detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus are
not limitative of the present invention, and wherein:
FIG. 1 is a circuit diagram of a conventional backlight on/off
control apparatus for an LCD TV; and
FIG. 2 is a circuit diagram of the automatic backlight on/off
control apparatus for an LCD TV according to the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now in detail to the drawings for the purpose of
illustrating preferred embodiments of the present invention, the
automatic backlight on/off control apparatus as shown in FIG. 2
comprises a buffer amplifier member 3 for buffer-amplifying and
integrating the composite video signals which enter a composite
video signal input terminal Vi, a synchronizing signal detecting
member 4 for detecting and outputting a synchronizing signal
according to the signal output level of the buffer amplifier member
3, a switching control member 5 for outputting a switching control
signal by integrating and differentially amplifying the output
signal of the synchronizing signal detecting member 4, and a
backlight voltage control member 6 for supplying or cutting off the
voltage of a backlight voltage terminal Vcc to the backlight 2 with
a switching operation in accordance with the switching control
signal of the switching control member 5.
The buffer amplifier member 3 is constructed by connecting the
composite video signal input terminal Vi to bias resistors R.sub.11
and R.sub.12 and a base of a transistor TR.sub.11 through a
coupling capacitor C.sub.11, connecting a emitter of the transistor
TR.sub.11 to a resistor R.sub.13, and connecting again the emitter
of the transistor TR.sub.11 to a capacitor C.sub.12 through a
resistor R.sub.14.
The synchronizing signal detecting member 4 is built by connecting
the connection point of the resistor R.sub.14 and capacitor
C.sub.12 through a resistor R.sub.15 and a capacitor C.sub.13 in a
parallel connection to the emitter of a transistor TR.sub.12 which
is supplied with a constant voltage through resistors R.sub.16 and
R.sub.17, connecting the emitter of a transistor TR.sub.13 applied
with a constant voltage through resistors R.sub.19 and R.sub.20 to
the base of a transistor TR.sub.14 as well as to a collector of the
transistor TR.sub.12 through a resistor R.sub.18, and connecting
the collector of the transistor TR.sub.14 to the base of a
transistor TR.sub.15 as well as to a resistor R.sub.24 and the
emitter of the transistor TR.sub.15 through a resistor
R.sub.23.
The switching control member 5 is constituted by connecting the
resistors R.sub.23 and R.sub.24 and the emitter of the transistor
TR.sub.15 to a capacitor C.sub.14 and the base of a transistor
TR.sub.16 of forming a darlington connection with a transistor
TR.sub.17, connecting the collectors of transistors TR.sub.20 and
TR.sub.21 in a darlington configuration supplied with a constant
voltage through resistors R.sub.26, R.sub.27, and R.sub.28 to the
bases of transistors TR.sub.18 and TR.sub.19 as a constant current
source and the collector of the transistor T.sub.18, connecting the
emitters of the transistors TR.sub.17 and TR.sub.21 to the
collector of a transistor TR.sub.22 supplied with a constant bias
voltage through the resistors R.sub.26, R.sub.27, and R.sub.28, and
connecting the collector of the transistor TR.sub.19 to a resistor
R.sub.25.
The backlight voltage control member 6 is formed by connecting a
connection point of the resistor R.sub.25 and the collector of the
transistor TR.sub.19 to the base of a transistor TR.sub.23,
connecting the emitter of the transistor TR.sub.23 to the base of a
transistor TR.sub.24 and a resistor R.sub.29 through a resistor
R.sub.30, and connecting the emitter of the transistor TR.sub.24 to
the backlight voltage terminal Vcc while connecting the collector
of the transistor TR.sub.24 to the primary winding of a transformer
T and the collector of the transistor TR.sub.1 being controlled by
the pulse generating member 1.
And, reference numeral 7 in FIG. 2 denotes a video signal display
member indicative of the video signal entering the composite video
signal input terminal Vi.
The operation and the effect of the configuration mentioned above
according to the present invention will be described below in
detail.
When a voltage is applied to a voltage terminal B.sup.+ and the
backlight voltage terminal Vcc, and the composite video signal is
inputted to the composite video signal input terminal Vi, the
composite video signal is applied to and displayed on a video
signal display member 7 through a resistor R.sub.10 and a capacitor
C.sub.10. Also, the composite video signal is buffer-amplified
through the transistor TR.sub.11 after the direct current component
of the signal is removed when the signal crosses the coupling
capacitor C.sub.11, the emitter output signal is charged in the
capacitor C.sub.12 through the resistor R.sub.14, the charged
voltage in the capacitor C.sub.12 is applied to the emitter of the
transistor TR.sub.12 through the resistor R.sub.15 and the
capacitor in a parallel connection in order for the transistor
TR.sub.12 to be controlled.
That is, the transistor TR.sub.12 is turned on in case there is a
lower voltage at the emitter of the transistor TR.sub.12 than a
bias voltage applied to the base of the transistor TR.sub.12
because of a constant bias voltage application to the base of the
transistor TR.sub.12 through resistors R.sub.16 and R.sub.17.
Accordingly, when a negative synchronizing signal is inputted to
the composite synchronizing signal input terminal Vi, a low level
signal is applied to the base of the transistor TR.sub.11 so that
the transistor TR.sub.11 is turned off, which causes the charged
voltage in the capacitor C.sub.12 to be discharged through
resistors R.sub.13 and R.sub.14.
Therefore, the voltage applied to the emitter of the transistor
TR.sub.12 becomes so lower than the bias voltage applied to the
base of the transistor TR.sub.12 that the transistor TR.sub.12 is
turned on. When the transistor TR.sub.12 is turned on, the
transistor TR.sub.13 is also turned on causing electric current
flow to the collector of the transistor TR.sub.12 through the
resistor R.sub.18. Therefore, the transistor TR.sub.14 is turned on
so that the collector of the transistor TR.sub.14 has a high
potential output. The voltage of the voltage terminal B.sup.+ is
rapidly charged in the capacitor C.sub.14 through the resistor
R.sub.22 and the transistor TR.sub.15 because the transistor
TR.sub.15 is turned on by the high potential. Thereafter, when the
transistor TR.sub.15 is turned off, the charged voltage of the
capacitor C.sub.14 is discharged slowly through the resistor
R.sub.24. Accordingly, in the situation for the composite
synchronizing signal to be applied to the composite synchronizing
signal input terminal Vi, the transistors TR.sub.16 and TR.sub. 17
are turned on and the transistors TR.sub.20 and TR.sub.21 are
turned off because the charged voltage of capacitor C.sub.14 keeps
above the determined voltage level higher than that divided by
resistors R.sub.26, R.sub.27, and R.sub.28. At this time, the
transistor TR.sub.22 is turned on because of the bias voltage
application to the base of the transistor TR.sub.22 through
resistors R.sub.26, R.sub.27, and R.sub.28. When the transistors
TR.sub.20 and TR.sub.21 keep the off-stage, the transistors
TR.sub.18 and TR.sub.19 are also turned off so that the base of the
transistor TR.sub.23 is applied with low potential. Therefore, the
transistor TR.sub.23 is turned on to output a low potential at the
emitter thereof so that the transistor TR.sub.24 is turned on. And
then the backlight voltage of the backlight voltage terminal Vcc is
applied to the collector of the transistor TR.sub.1 and the primary
winding of the transformer T through the transistor TR.sub.24.
Accordingly, as shown in FIG. 1, when the transistor TR.sub.1 is
turned on or off according to the pulse signals of the pulse
generating member 1, the voltage of the backlight voltage terminal
Vcc is induced in the second winding of the transformer T, which
causes a capacitor C.sub.1 to be charged. The charged voltage of
the capacitor C.sub.1 is applied to the backlight 2 through a
capacitor C.sub.2 to turn the backlight 2 on. On the other hand, in
case the composite video signal is not inputted to the composite
video signal input terminal Vi, the transistor TR.sub.11 is turned
on by the bias voltage through resistors R.sub.11 and R.sub.12 so
that the emitter of the transistor TR.sub.11 keeps a high
potential. This high potential is charged in the capacitor C.sub.12
through the resistor R.sub.14. The charged voltage of the capacitor
C.sub.12 makes the voltage applied to the emitter of the transistor
TR.sub.12 higher than that applied to the base of the transistor
TR.sub.12. Therefore, the transistor TR.sub.12 is turned off.
As a result, the transistor TR.sub.13 is also turned off, the base
of the transistor TR.sub.14 is applied with a high potential and
the transistor TR.sub.14 is turned off, causing the transistor
TR.sub.15 to be kept off. Therefore, the base of the transistor
TR.sub.16 is applied with a low potential.
At this time, the transistors TR.sub.16 and TR.sub.17 are turned
off since the voltage applied to the base of the transistor
TR.sub.20 through the resistors R.sub.26, R.sub.27, and R.sub.28
becomes higher than that applied to the base of the transistor
TR.sub.16 causing the transistors TR.sub.20 and TR.sub.21 to be
kept on. And the transistor TR.sub.22 is turned on by the bias
voltage through the resistors R.sub.26, R.sub.27, and R.sub.28,
which causes the transistors TR.sub.18 and TR.sub.19 as a constant
current source to be turned on. When the transistor TR.sub.18 is
turned on, the collector of the transistor TR.sub.19 has a high
potential causing the transistor TR.sub.23 to be turned off.
Therefore, the transistor TR.sub.24 is turned off by the high
potential at the emitter of the transistor TR.sub.19.
When the transistor TR.sub.24 is turned off, the backlight 2 is
kept off because the backlight voltage of the backlight voltage
terminal Vcc applied to the collector of the transistor TR.sub.1
and the primary winding of the transformer T is cut off.
As mentioned above in detail, the present invention has the effect
that prevents the unnecessary electric power consumption by turning
the backlight 2 off in case there is no input of any video signal
and turning the backlight 2 on according to the pulse signals of
the pulse generating member 1 only in case there is a video signal
input.
The invention being thus described, it will be obvious that the
same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included in the scope of the following
claims.
* * * * *